In 1977 the Big Black motor company decided it was about time to take a stab at the trolling motor industry. Why not? They had a pretty good market share of the outboard industry at the time – they might as well try and get some of the electric motor market too.
A first look at the motor and one could see it was different than any other electric motor on the market due to the giant propeller. In fact, the prop was in some cases twice as big as any other trolling motor prop in the industry. The concept was simple, with more blade surface area and pitch, the prop didn’t have to turn as fast as smaller props on the market to go the same distance. Hence, in theory, the motor didn’t have to work as hard and this would save your batteries.
Mercury touted that their 12-volt trolling motors put out as much thrust as any 24-volt competitor’s motors – and they did. Rig your boat with two batteries dedicated to the trolling motor and you could go all day in some pretty severe conditions without any worry of your batteries dying.
The downfall of the Merc Thruster, though, was in its noise. The gear reduction system employed literally sounded like a barista grinding coffee beans. Where you made up in thrust and battery life, you lost it in your ability to sneak up on fish in shallow water. This was when they were new. After a couple of trips, where your prop had the misfortune of hitting a rock or stump, the sound got louder and louder. Growing up in the West where we normally had 30-foot water visibility, I always cringed when I drew someone who had a Thruster on their boat.
Another interesting bit of information that I never really paid attention to was stated in the ad on page 4, bottom right. Under Propeller, Mercury talks about the prop being designed to minimize weed fouling. Although they claim the weedless properties of the prop are due to the blades being swept back, which it may have some effect, this was the first prop developed, that I can recall, that had a shaft the same diameter as the head.
As many of you know, it was the Bass Professor Doug Hannon who developed and received the patent on the first weedless prop in 1980 (click here to see his YouTube video on the development of the weedless prop). After reading this ad, I wonder if Hannon looked at the design of this prop and used it to help develop his. Hannon’s prop was different in that the prop shaft did not taper down from the head of the motor to the back – it was a constant diameter. Not only that, Hannon’s prop had much smaller blades.
Mercury went on and produced the Thruster for probably 15 years. Although they had a great concept for a trolling motor in the beginning, companies like Minn-Kota, Motor Guide and OMC continued to dominate trolling motor sales. Then eventually Mercury gave up on their own baby and bought Motor Guide. I guess if you can’t beat them, you might as well buy them.